In recent years, a fiber-optic processing has been developed by using a semiconductor laser and optical fibers to carry out works such as soldering or the like.
As the first example, a conventional fiber-optic processing equipment is disclosed that has: a laser diode element (not shown, hereafter referred to as an LD element); one optical fiber (single fiber) 113; and condenser lens 106 as shown in FIG. 6. The equipment allows a light beam emitted from the LD element to enter into optical fiber 113 to be guided to a predetermined position to carry out for instance soldering component parts on a printed circuit board by irradiating the light beam from optical fiber 113 to be focused on a soldering area by condenser lens 106.
As the second example, another conventional fiber-optic processing equipment is disclosed in Unexamined Japanese Patent Publication No. H02-142695 that has: a plurality of LD elements 105; fiber-bundle 114 including a plurality of optical fibers 123; and condenser lens 106. The equipment allows each light beam emitted from LD element to enter into optical fiber 123 to be guided to a predetermined position to carry out for instance soldering component parts on a printed circuit board by irradiating the light beam from optical fiber 123 to be focused on a soldering area by condenser lens 106.
To solder component parts on a printed circuit board, lead (conductive pin) 110 of component parts 109 is inserted into through-hole 108, and allowing them to stand for a while, soldering areas such as land 107 and lead 110 of the component parts are needed to be irradiated for preheating to improve solder wettability. In the first example of the conventional fiber-optic processing equipment, the light beam irradiation pattern on a soldering area for the preheating is formed of a shape similar to single fiber 113 or a round shape as shown in FIG. 9. Since the light beam irradiates the whole circle as shown in FIG. 6, a portion of the irradiation have reached a surface of component parts 109, or an area indicated by circle 120, via through-hole 108, causing a problem on component parts 109.
Additionally, using fiber-bundle 114 composed of a plurality of optical fibers 123 as shown in FIG. 10 will also cause the same problem, if whole cross-sectional area of fiber-bundle 114 is fully occupied by optical fibers. That is, as shown in FIG. 8, a portion of irradiation light beam will reach a surface of component parts 109 or an area indicated by circle 120 via through-hole 108, causing a problem on component parts 109.
Contrarily, in the second example of the conventional fiber-optic processing equipment, it is described that a wide variety of irradiation patterns can be selected by changing the bundle configuration of fiber-bundle 114 used for the equipment. In this way, the above problems can be solved by changing the focusing patterns of light beam for instance into annular or doughnut shaped.
In this case, however, a plurality of fiber-bundles 114 having annular irradiation area and with different irradiation diameters are needed to be prepared for replacement with respect to shapes of processing objectives, causing problems in production cost and workability. To measure the problem a configuration is proposed in which optical fibers 123 are provided in whole cross-sectional area of fiber-bundle 114 and output of each optical fiber 123 is controlled individually as shown in FIG. 10, enabling fiber-bundle 114 to have an annular irradiation pattern whose ring diameter can be variable, thereby resulting in no need of replacing fiber-bundle 114 with respect to each processing objective. The configuration, however, is not economical since fiber-bundle 114 needs a large number of optical fibers 123 extra and also needs additional structure to control output of each optical fiber 123, causing a complicated structure and an increase in production cost. Moreover, a problem in this case is that the irradiation area can be adjusted only discretely but not continuously or finely since a ring diameter of the irradiation pattern is restricted by the clearance with which optical fibers are disposed. The irradiation area should be adjusted finely in precision soldering.